Starting Tor Browser 8 is broken on some older Linux systems

We have reports from Linux Mint 17 and Ubuntu 14 users that Tor Browser is not starting anymore, probably due to #25485 (moved). The error they get is:

./firefox.real: relocation error: ./firefox.real: symbol _ZTTNSt7__cxx1119basic_ostringstreamIcSt11char_traitsIcESaIcEEE, version GLIBCXX_3.4.21 not defined in file libstdc++.so.6 with link time reference

There is a workaround posted (https://blog.torproject.org/comment/276770#comment-276770)

1 open file /Browser/firefox
2 comment line 10,12( if and fi) to use custom libstdc++
#if [ $? -ne 0 ]; then
LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$basedir/TorBrowser/Tor/libstdc++/"
#fi

So, it seems our abicheck hack is not working as expected? I wonder what is going on here, though, as I have no issues updating from 7.5.6 to 8.0 on an Ubuntu 14.04.